The overall goal of this project is to understand the regulatory mechanisms which control the processes of exocrine protein secretion. Structural and functional characterization of purified salivary proteins has provided ample evidence for salivary proteins to play important roles in the oral host defense system. Such structure/function studies indicate that posttranslational processing such as proteolytic events, phosphorylation and glycosylation are of functional significance but very little is known how these steps are controlled and how they affect the structural and functional domains of specific secretory proteins. The principal steps in the regulatory secrtoty pathway are protein synthesis, storage and packaging of proteins in secretory vesicles and stimulus-dependent exocytosis. Recent work in our laboratory succeeded in the development of several orgnic boron compounds representing a novel tool for the investigation of secretory mechanisms. These compounds have been shown to affect in specific but different ways constitutive secretion of hepatoma cells and regulated secretion of rat parotid glands. The specific aims are: I. Characterization of biosynthesis, posttranslational processing and secretion of salivary proteins in the rat parotid gland in terms of a) secretory protein profile, b) postranslational modifications, c) kinetics of secretion, and d) differentiation between constitutive and regulated pathway. II. Modulation of parotid secretion by a) known inhibitors of constitutive secretion, b) by boronate compounds in terms of synthesis, processing and exocytosis. III. Analysis of the secretion of parotid proteins by Xenopus oocytes injected with rat parotid mRNA. IV. Isolation and characterization of selected rat parotid proteins to a) describe in molecular terms the effect(s) of modulators of protein synthesis, processing and secretion, and b) to establish the relevance of observations made in the rat model to human secretory proteins. The long term goal of this work is to understand secretory mechanisms at the molecular level, providing the basis for possible targeted control of salivary and as well as other secretions.